1. Field of the Invention
Our invention relates to liquid atomizing devices. In particular, our invention relates to an improved liquid atomizing device, for atomizing liquids to disperse droplets thereof into the ambient air, which is able to reduce the amount of atomized liquid droplets that fall onto proximate surfaces by increasing the evaporation rate of the atomized liquid.
2. Description of the Related Art and Problem to Be Solved
Devices that release vapors into the ambient air are well-known in the art. The purpose of these devices may be to deodorize, disinfect, or impart a desired fragrance to the ambient air, to deliver a medical or cosmetic spray, to humidify, or to distribute toxins into the air to kill or to repel unwanted pests, such as insects.
Several methods have been employed to dispense vapors into the air. For example, some methods utilize the evaporative properties of liquids, or of other vaporizable materials, to cause vapors with desired properties to be distributed into the ambient air. One such evaporative method utilizes a wick to deliver a vaporizable liquid from a reservoir to a surface exposed to the ambient air, from which surface the liquid is vaporized and dispersed into the air. Other methods, however, involve atomizing the liquid—that is, reducing the liquid into tiny particles that are dispersed into the air as a fine spray.
U.S. Pat. No. 6,293,474 B1 to Helf et al., assigned to the assignee of this application, describes an example of a device for dispensing liquids as an atomized spray. This patent is incorporated in its entirety in this description by reference. Helf et al. discloses the production of a fine spray of liquid droplets using a continuous action dispenser having an orifice plate in communication with a piezoelectric element which expands and contracts when alternating voltages are applied thereto. A wick delivers liquid to be atomized from a container to the orifice plate, and the vibration of the orifice plate, communicated by the piezoelectric element, causes droplets to be ejected into the air. This system achieves preferred dispensing of the liquid.
However, with atomization devices, a potential problem is that the atomized liquid droplets can settle back onto the device, and/or onto surfaces around the device, before they completely evaporate. This problem can be of particular concern, for example, with respect to insect control or air-freshening liquid formulations because such formulations often contain strong solvents that are harmful to surfaces, especially surfaces with fine lacquered wood finishes. Consumers often place liquid atomizing devices on such surfaces (e.g., on wooden furniture such as a table or a dresser), and when atomized liquid droplets fail to evaporate, and instead settle down onto the adjacent surfaces, the droplets can cause the finish on the surfaces to be damaged, among other unwanted effects.
To address this concern, changing the character of the dispensed liquid has been suggested. For example, the specific formulation of the dispensed liquid might be altered so that the liquid will not act as a furniture-stripping agent if it comes in contact with a finished wooden surface. This approach, however, can limit the selection of liquid components that can be used, especially the selection of usable fragrance components.
But even when the particular composition of the liquid formulation in a device is not necessarily damaging to a given surface, the accumulation of droplets on a surface can still be bothersome. For example, a plastic surface or a glass surface that does not react with the liquid formulation must still be cleaned by the user of the device after droplets have collected on that surface. As another example, a particular liquid formulation might not actually harm an area of carpet fibers or a fabric surface, but it could still be a nuisance due to being absorbable into the carpet or fabric.
Also of concern is that droplets can settle back onto the liquid atomizing device itself, presenting a nuisance and/or adversely affecting further atomization and efficient dispersion, such as by clogging the orifices through which the atomized liquid droplets are ejected into the air.
Accordingly, in a liquid atomizing device, there is a need to minimize the amount of atomized liquid droplets that fail to evaporate fully before settling down on the device and/or surrounding surfaces. It is part of our invention to include such features in an improved liquid atomizing device.
While it has previously been suggested that liquid atomizing devices can include a heater, a fan, or both a heater and a fan, we believe that such earlier devices do not use heaters and/or fans to solve the problems of the prior art as our invention does.
For instance, U.S. Pat. No. 6,378,988 B1 to Taylor et al. relates to a replaceable cartridge for micro jet dispensing assemblies containing a micro jet piezoelectric ejector. In this device, the piezoelectric ejector ejects micro-droplets of volatile fluids onto a heatable surface, wetting the heatable surface. This heatable surface aids in volatilization of the fluid.
U.S. Pat. No. 6,062,212 to Davison et al. teaches a dispensing apparatus that disperses an atomized spray through an outlet. Specifically, a droplet of liquid is metered onto a membrane which is vibrated by a piezoelectric transducer such that atomized droplets are dispensed through holes formed in the membrane. In one embodiment of that invention, an electric fan is provided at one end of a duct into which droplets are dispensed as an aerosol mist. The fan creates a flow of air that helps to deliver the mist atraumatically to an eye engaged with an eye cup at the opposite end of the duct.
U.S. Pat. No. 6,371,451 B1 to Choi teaches a scent diffusion method. In a scent-spraying unit, scents in scent cartridges are dispensed through piezoelectric-type or thermal jet spray-type spraying nozzles into an evaporation dish provided with a heater. An exhaust fan is driven to discharge the evaporated scent from the unit. According to this patent, it is preferable that a residual liquid scent is inhaled upon termination of each spraying operation, in order to prevent the spraying nozzles from being clogged.
U.S. Pat. No. 6,390,453 B1 to Frederickson et al. discloses a method and an apparatus that employ a pulse-controlled micro-droplet fluid delivery system for precisely dispensing fragrances and other odor-producing vapors. In one embodiment, a print head dispenses droplets directly onto the heated surface of a heater, wetting the heater. The apparatus includes a blower, adjacent to the heater, which creates air flow that carries vapor through an air-flow channel leading to the outside of the apparatus.
In another embodiment, a target medium intercepts droplets as they are dispensed approximately sideways, toward the outlet of the apparatus. A blower in the apparatus is mounted in a housing containing a heating element. This assembly warms and heats the air being moved, which, together with the vapor produced by evaporation of the dispensed droplets, proceeds through the target medium to an air-flow outlet.
U.S. Pat. No. 6,554,203 B2 to Hess et al. relates to a smart miniature fragrance-dispensing device for multiple ambient scenting applications and environments. Within the device, a liquid spray dispenser dispenses droplets of a principal medium into a flow channel, which is a controllable induced mixed media flow channel for mixing the principal medium with an ambient medium contained within the flow channel. The flow channel, which has heaters in the form of flow inducing elements, expels the mixed media through an outlet into the environment. The device has a piezoelectric driving circuit for exciting a piezoelectric element, to dispense droplets from the liquid spray dispenser.
U.S. Pat. No. 6,405,934 B1 to Hess et al., which relates to an optimized liquid droplet spray device for an inhaler suitable for respiratory therapies, describes a spray device with a chamber for containing a liquid formed of a top substrate and a bottom substrate. The top substrate has outlet means consisting of cavities, outlet nozzles, and outlet channels. A piezoelectric element disposed beneath the bottom substrate constitutes vibrating means and can also act as a heater. A separate flexible heating surface, fitted on the two substrates, can also be included in the spray device.
While these documents describe various combinations of piezoelectric-type atomizing devices, heaters, and fans for dispensing volatile substances, none of these patents adequately teaches suitable improvements for minimizing the amount of atomized liquid droplets that settle on the device and/or its surrounding surfaces by increasing the evaporation rate of dispensed droplets, in the manners set forth below.